As we previously stated [33] and [43], carboxylic groups play multiple roles in the synthesis of Ag NCs and one of them is as a host of Ag ions. Therefore, it is necessary to evaluate the pH effect on Ag NC formation, since it controls the extent of deprotonation of carboxylic groups and will influence the binding ability of carboxylic groups. When the pH is in the range of 5.04–8.34, carboxylic groups are completely deprotonated and it is favorable for the formation of Ag NCs [33]. For the pH of 5.62 (the original pH of AgNO3), the maximum luminescence intensity is observed (shown in Fig. 4a), indicating the highest yield of Ag NCs. There are no Ag NCs forming when the pH is lower than 4.88. When the pH is higher than 6.89, we can conclude that the solution became basic and its color turned from colorless to brown, indicating the formation of AgOH precipitates, which could account for the decrease of luminescence intensity.
As we previously stated [33] and [43], carboxylic groups play multiple roles in the synthesis of Ag NCs and one of them is as a host of Ag ions. Therefore, it is necessary to evaluate the pH effect on Ag NC formation, since it controls the extent of deprotonation of carboxylic groups and will influence the binding ability of carboxylic groups. When the pH is in the range of 5.04–8.34, carboxylic groups are completely deprotonated and it is favorable for the formation of Ag NCs [33]. For the pH of 5.62 (the original pH of AgNO3), the maximum luminescence intensity is observed (shown in Fig. 4a), indicating the highest yield of Ag NCs. There are no Ag NCs forming when the pH is lower than 4.88. When the pH is higher than 6.89, we can conclude that the solution became basic and its color turned from colorless to brown, indicating the formation of AgOH precipitates, which could account for the decrease of luminescence intensity.
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